Process for recycling cyclopentadienyl derivatives and preparing metallocenes from recycled, substituted cyclopentadienyl derivatives

ABSTRACT

The present invention relates to a process for recycling cyclopentadienyl derivatives of the formulae (I) and (I′), a process for preparing metallocenes of the formula (III) from cyclopentadienyl derivatives of the formulae (I) and (I′) or from bridged biscyclopentadienyl derivatives of the formula (II), in which the cyclopentadienyl derivatives of the formulae (I), (I′) or (II) which are used have been at least partly recovered and purified by means of liquid-solid chromatography, and the use of liquid-solid chromatography for purifying substituted, recovered cyclopentadienyl derivatives of the formulae (I), (I′) or (II).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national phase filing under 35 U.S.C. §371 ofInternational Application PCT/EP2006/012234, filed 19 Dec. 2006,claiming priority to German Patent Application 102005061326.8 filed 20Dec. 2005 and provisional U.S. Appl. No. 60/787,453 filed 30 Mar. 2006;the disclosures of International Application PCT/EP2006/012234, GermanPat. Appl. 102005061326.8, and U.S. Appl. No. 60/787,453, each as filed,are incorporated herein by reference.

The present invention relates to a process for recyclingcyclopentadienyl derivatives of the formulae (I) and (I′), a process forpreparing metallocenes of the formula (III) from cyclopentadienylderivatives of the formulae (I) and (I′) or from bridgedbiscyclopentadienyl derivatives of the formula (II), in which thecyclopentadienyl derivatives of the formulae (I), (I′) or (II) which areused have been at least partly recovered and purified by means ofliquid-solid chromatography, and the use of liquid-solid chromatographyfor purifying substituted, recovered cyclopentadienyl derivatives of theformulae (I), (I′) or (II).

In the past 15 years, research and development on the use of organictransition metal compounds, in particular metallocenes, as catalystcomponents for the polymerization and copolymerization of olefins hasbeen pursued intensively in universities and in industry with theobjective of preparing tailored polyolefins. Now, not only theethylene-based polyolefins prepared by means of metallocene catalystsystems but also, in particular, the propylene-based polyolefinsprepared by means of metallocene catalyst systems represent adynamically growing market segment.

In the preparation of polyolefins, in particular in the preparation ofisotactic polypropylenes, metallocenes whose substitutedcyclopentadienyl ligands are prepared in a plurality of syntheses areused. The preparation of substituted cyclopentadienyl ligands isdescribed, for example, in EP 0 576 970, WO 1998/40331, WO 1999/24446,WO 2001/47939, WO 2001/48034, WO 2002/092564, WO 2003/014107 or WO2003/045964.

Metallocenes which are used for preparing isotactic polypropylenes areusually bridged racemic metallocenes having substituted cyclopentadienylligands prepared by a complicated synthesis. In the synthesis of racemicansa-metallocenes, these are generally obtained together with theundesirable meso-metallocenes which usually have to be separated off, sothat part of the costly ligand which has not been converted into thedesired racemic metallocene is inevitably lost. To minimize the loss ofthe costly starting materials, various diastereoselective syntheticmethods in which the proportion of the desired racemic metallocene ishigher than the proportion of the undesirable meso form have beendeveloped. Such racemoselective processes are described, for example, inWO 1999/15538 or WO 2005/108408.

WO 2002/96920 describes a process for purifying racemic metallocenes byremoving the by-products formed in the preparative process, with atleast part of the bridged biscyclopentadienyl ligand which has not beenconverted into the desired product being recovered from the filtrates bycrystallization.

Despite the progress achieved to date in the optimization of themetallocene synthesis in respect of the yield of the desired metallocenebased on the ligand precursors used, there continues to be a need toimprove the economics of the metallocene syntheses.

It was therefore an object of the present invention to discover abroadly applicable process for preparing metallocenes which improves theeconomics of the preparative process compared to the prior art.

We have accordingly found a process for recycling substitutedcyclopentadienyl derivatives of the formulae (I) and (I′)

and/or their double bond isomers,or bridged biscyclopentadienyl derivatives of the formula (II)

and/or their double bond isomers,where

-   R¹, R^(1′) are identical or different and are each an organic    radical having from 1 to 40 carbon atoms,-   R², R^(2′) are identical or different and are each hydrogen or an    organic radical having from 1 to 40 carbon atoms, or-   R¹ with R² and/or R^(1′) with R^(2′) together with the atoms    connecting them in each case form a monocyclic or polycyclic,    saturated or unsaturated, substituted or unsubstituted ring system    which has from 3 to 40 carbon atoms and has a ring size of from 5 to    12 atoms and may also comprise heteroatoms selected from the group    consisting of the elements Si, Ge, N, P, As, Sb, O, S, Se or Te,-   T, T′ are identical or different and are each a divalent organic    group which has from 1 to 40 carbon atoms and together with the    cyclopentadienyl ring in each case forms at least one further    saturated or unsaturated, substituted or unsubstituted ring system    having a ring size of from 5 to 12 atoms, where T and T′ within the    ring system fused to the cyclopentadienyl ring may comprise the    heteroatoms Si, Ge, N, P, As, Sb, O, S, Se or Te,-   Z is a bridge between the two substituted cyclopentadienyl ligands    which consists of a divalent atom or a divalent group,    wherein the cyclopentadienyl derivatives of the formulae (I) and    (I′) and/or their double bond isomers or the bridged    biscyclopentadienyl derivatives of the formula (II) and/or their    double bond isomers which are used in the preparative process have    been at least partly recovered from the filtrates, mother liquors,    reaction residues and/or work-up residues obtained in the    preparation of metallocenes and/or in the preparation of bridged    biscyclopentadienyl ligands and subsequently purified by means of    liquid-solid chromatography.

We further found a process for preparing metallocenes of the formula(III)

wherein

-   M is an element of group 3, 4, 5 or 6 of the Periodic Table of the    Elements or the lanthanides,-   the radicals X are identical or different and are each an organic or    inorganic radical, with two radicals X also being able to be joined    to one another,-   n is 0, 1, 2 or 3, and-   m is 0 or 1,    including the process for recycling substituted cyclopentadienyl    derivatives of the formulae (I) and (I′) and/or their double bond    isomers, or bridged biscyclopentadienyl derivatives of the    formula (II) and/or their double bond isomers,

The radicals R¹ and R^(1′) are identical or different, preferablydifferent, and are each an organic radical having from 1 to 40 carbonatoms, for example C₁-C₄₀-alkyl, C₁-C₁₀-fluoroalkyl, C₂-C₄₀-alkenyl,C₆-C₄₀-aryl, C₆-C₁₀-fluoroaryl, arylalkyl, arylalkenyl or alkylarylhaving from 1 to 10, preferably from 1 to 4, carbon atoms in the alkylradical and from 6 to 22, preferably from 6 to 10, carbon atoms in thearyl radical, or a C₂-C₄₀-heteroaromatic radical which has at least oneheteroatom selected from the group consisting of the elements O, N, S, Pand Se, in particular O, N and S, and may be substituted by furtherradicals R³, where R³ is an organic radical having from 1 to 20 carbonatoms, for example C₁-C₁₀-, preferably C₁-C₄-alkyl, C₆-C₁₅-, preferablyC₆-C₁₀-aryl, alkylaryl, arylalkyl, fluoroalkyl or fluoroaryl each havingfrom 1 to 10, preferably from 1 to 4, carbon atoms in the alkyl radicaland from 6 to 18, preferably from 6 to 10, carbon atoms in the arylradical, and a plurality of radicals R³ may be identical or different.

Preference is given to R¹ and R^(1′) being identical or different,preferably different, and each being C₁-C₁₀-alkyl such as methyl, ethyl,n-propyl, isopropyl, n-butyl, i-butyl, s-butyl, t-butyl, n-pentyl,cyclopentyl, n-hexyl, cyclohexyl, n-heptyl or n-octyl, preferablymethyl, ethyl or isopropyl.

The radicals R² and R^(2′) are identical or different, preferablyidentical, and are each hydrogen or an organic radical having from 1 to40 carbon atoms, for example C₁-C₄₀-alkyl, C₁-C₁₀-fluoroalkyl,C₂-C₄₀-alkenyl, C₆-C₄₀-aryl, C₆-C₁₀-fluoroaryl, arylalkyl, arylalkenylor alkylaryl having from 1 to 10, preferably from 1 to 4, carbon atomsin the alkyl radical and from 6 to 22, preferably from 6 to 10, carbonatoms in the aryl radical, or a C₂-C₄₀-heteroaromatic radical which hasat least one heteroatom selected from the group consisting of theelements O, N, S, P and Se, in particular O, N and S and may besubstituted by further radicals R³ as defined above and a plurality ofradicals R³ may be identical or different. R² and R^(2′) are preferablyhydrogen.

As an alternative, R¹ with R² and/or R^(2′) with R^(2′) together withthe atoms connecting them in each case form a monocyclic or polycyclic,saturated or unsaturated, substituted or unsubstituted ring system whichhas from 3 to 40 carbon atoms and a ring size of from 5 to 12, inparticular from 5 to 7, atoms and may also comprise heteroatoms selectedfrom the group consisting of the elements Si, Ge, N, P, As, Sb, O, S, Seor Te, preferably Si, N, O or S, in particular S or N.

Examples of preferred, joined radicals R¹/R² and/or R^(1′)/R^(2′) are

preferably

in particular

wherethe radicals R⁴ are identical or different and are each an organicradical having from 1 to 40, preferably from 1 to 20, carbon atoms, forexample a cyclic, branched or unbranched C₁-C₂₀-, preferably C₁-C₈-alkylradical, C₂-C₂₀-, preferably C₂-C₈-alkenyl radical, C₆-C₂₂-, preferablyC₆-C₁₀-aryl radical, an alkylaryl or arylalkyl radical having from 1 to10, preferably from 1 to 4, carbon atoms in the alkyl radical and from 6to 22, preferably from 6 to 10, carbon atoms in the aryl radical, wherethe radicals may also be halogenated, or the radicals R⁴ are substitutedor unsubstituted, saturated or unsaturated, in particular aromaticheterocyclic radicals which have from 2 to 40, in particular from 4 to20 carbon atoms and may comprise at least one heteroatom which ispreferably selected from among the group of elements consisting of O, N,S and P, in particular O, N and S,R⁵ is hydrogen or is as defined for R⁴,or two adjacent radicals R⁴ or R⁴ with R⁵ together with the atomsconnecting them form a monocyclic or polycyclic, substituted orunsubstituted ring system which has from 3 to 40 carbon atoms and mayalso comprise heteroatoms selected from the group consisting of theelements Si, Ge, N, P, O, S, Se and Te, in particular N or S,the indices s are identical or different and are each a natural numberfrom 0 to 4, in particular from 0 to 3,the indices t are identical or different and are each a natural numberfrom 0 to 2, in particular 1 or 2, andthe indices u are identical or different and are each a natural numberfrom 0 to 6, in particular 1.T and T′ are identical or different, preferably identical, and are eacha divalent organic group which has from 1 to 40 carbon atoms andtogether with the cyclopentadienyl ring forms at least one furthersaturated or unsaturated, substituted or unsubstituted ring systemhaving a ring size of from 5 to 12, in particular from 5 to 7, atoms,with T and T′ within the ring system fused to the cyclopentadienyl ringbeing able to comprise the heteroatoms Si, Ge, N, P, As, Sb, O, S, Se orTe, preferably Si, N, O or S, in particular S or N.

Examples of preferred divalent organic groups T or T′ are

preferably

in particular

whereR⁴, R⁵, s, t and u are as defined above.Z is a bridge between the two substituted cyclopentadienyl rings whichconsists of a divalent atom or a divalent group. Examples of Z are:

-   -   —B(R⁷)—, —B(NR⁷R⁸)—, —Al(R⁷)—, —O—, —S—, —S(O)—, —S((O)₂)—,        —N(R⁷)—, —C(O)—, —P(R⁷)— or —P(O) (R⁷)—,        in particular

whereM¹ is silicon, germanium or tin, preferably silicon or germanium,particularly preferably silicon, andR⁷, R⁸ and R⁹ are identical or different and are each a hydrogen atom, ahalogen atom, a trimethylsilyl group, a C₁-C₁₀-, preferably C₁-C₃-alkylgroup, a C₁-C₁₀-fluoroalkyl group, a C₆-C₁₀-fluoroaryl group, aC₆-C₁₀-aryl group, a C₁-C₁₀-, preferably C₁-C₃-alkoxy group, aC₇-C₁₅-alkylaryloxy group, a C₂-C₁₀-, preferably C₂-C₄-alkenyl group, aC₇-C₄₀-arylalkyl group, a C₈-C₄₀-arylalkenyl group or a C₇-C₄₀-alkylarylgroup or two adjacent radicals together with the atoms connecting themform a saturated or unsaturated ring having from 4 to 15 carbon atoms.

Preferred embodiments of Z are the bridges:

dimethylsilanediyl, methylphenylsilanediyl, methyl-tert-butylsilanediyl,diphenylsilanediyl, dimethylgermanediyl, in particulardimethylsilanediyl.

M is an element of group 3, 4, 5 or 6 of the Periodic Table of theElements or the lanthanides, preferably an element of group 4 of thePeriodic Table of the Elements, e.g. titanium, zirconium or hafnium,particularly preferably zirconium or hafnium, in particular zirconium.

The radicals X are identical or different, preferably identical, and areeach an organic or inorganic radical, with two radicals X also beingable to be joined to one another. In particular, X is halogen, forexample fluorine, chlorine, bromine, iodine, preferably chlorine,hydrogen, C₁-C₂₀-, preferably C₁-C₄-alkyl, C₂-C₂₀-, preferablyC₂-C₄-alkenyl, C₆-C₂₂-, preferably C₆-C₁₀-aryl, an alkylaryl orarylalkyl group having from 1 to 10, preferably from 1 to 4, carbonatoms in the alkyl radical and from 6 to 22, preferably from 6 to 10,carbon atoms in the aryl radical, —OR^(d) or —NR^(d)R^(e), preferably—OR^(d) or —NHR^(d), with two radicals X also being able to be joined toone another, preferably two radicals —OR^(d) which, in particular, forma substituted or unsubstituted 1,1′-di-2-phenoxide radical. Two radicalsX can also form a substituted or unsubstituted diene ligand, inparticular a 1,3-diene ligand. The radicals R^(d) and R^(e) are C₁-C₁₀-,preferably C₁-C₄-alkyl, C₆-C₁₅-, preferably C₆-C₁₀-aryl, alkylaryl,arylalkyl, fluoroalkyl or fluoroaryl each having from 1 to 10,preferably from 1 to 4, carbon atoms in the alkyl radical and from 6 to22, preferably from 6 to 10, carbon atoms in the aryl radical and R^(e)may also be hydrogen. Very particular preference is given to X beingchlorine or methyl, in particular chlorine.

The index n is 0, 1, 2 or 3, with n+2 usually corresponding to theoxidation number of M, and in the case of the elements of group 4 of thePeriodic Table of the Elements n is usually preferably 2. When M ischromium, n is preferably 0 or 1, in particular 0.

The index m is 0 or 1, preferably 1.

In the preparative process of the invention, use is made ofcyclopentadienyl derivatives of the formulae (I) and (I′) and/or theirdouble bond isomers or bridged biscyclopentadienyl derivatives of theformula (II) and/or their double bond isomers, in particularcyclopentadienyl derivatives of the formulae (I) and (I′) and/or theirdouble bond isomers, which have been at least partly recovered from thefiltrates, mother liquors, reaction residues and/or work-up residuesobtained in the preparation of metallocenes and/or in the preparation ofbridged biscyclopentadienyl ligands and subsequently purified by meansof liquid-solid chromatography, with the proportion of recovered, i.e.recycled, cyclopentadienyl derivatives of the formulae (I) and (I′)and/or their double bond isomers or bridged cyclopentadienyl derivativesof the formula (II) and/or their double bond isomers in the metallocenesynthesis preferably being at least 5%, preferably at least 10%,particularly preferably at least 25%.

The cyclopentadienyl derivatives of the formulae (I) and (I′) can havean identical or different substitution pattern in accordance with theabove description. The process of the invention thus relates to thepreparation of metallocenes having two identical cyclopentadienylligands or two different cyclopentadienyl ligands.

Furthermore, the substituents according to the present invention are,unless restricted further, defined as follows:

The term “organic radical having from 1 to 40 carbon atoms” as used inthe present text refers to, for example, C₁-C₄₀-alkyl radicals,C₁-C₁₀-fluoroalkyl radicals, C₁-C₁₂-alkoxy radicals, saturatedC₃-C₂₀-heterocyclic radicals, C₈-C₄₀-aryl radicals,C₂-C₄₀-heteroaromatic radicals, C₈-C₁₀-fluoroaryl radicals,C₆-C₁₀-aryloxy radicals, C₃-C₁₈-trialkylsilyl radicals, C₂-C₂₀-alkenylradicals, C₂-C₂₀-alkynyl radicals, C₂-C₄₀-arylalkyl radicals orC₈-C₄₀-arylalkenyl radicals. An organic radical is in each case derivedfrom an organic compound. Thus, the organic compound methanol can inprinciple give rise to three different organic radicals having onecarbon atom, namely methyl (H₃C—), methoxy (H₃C—O—) and hydroxymethyl(HOC(H₂)—).

The term “alkyl” as used in the present text encompasses linear orsingly or multiply branched saturated hydrocarbons which may also becyclic. Preference is given to C₁-C₁₈-alkyl such as methyl, ethyl,n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl,n-decyl, cyclopentyl, cyclohexyl, isopropyl, isobutyl, isopentyl,isohexyl, sec-butyl or tert-butyl.

The term “alkenyl” as used in the present text encompasses linear orsingly or multiply branched hydrocarbons having one or more C—C doublebonds, which may be cumulated or alternating.

The term “saturated heterocyclic radical” as used in the present textrefers to, for example, monocyclic or polycyclic, substituted orunsubstituted hydrocarbon radicals in which one or more carbon atoms, CHgroups and/or CH₂ groups are replaced by heteroatoms preferably selectedfrom the group consisting of O, S, N and P. Preferred examples ofsubstituted or unsubstituted saturated heterocyclic radicals arepyrrolidinyl, imidazolidinyl, pyrazolidinyl, piperidyl, piperazinyl,morpholinyl, tetrahydrofuranyl, tetrahydropyranyl, tetrahydrothiophenyland the like, and also methyl-, ethyl-, propyl-, isopropyl- and/ortert-butyl-substituted derivatives thereof.

The term “aryl” as used in the present text refers to, for example,aromatic and optionally also fused polyaromatic hydrocarbons which maybe monosubstituted or polysubstituted by linear or branchedC₁-C₁₈-alkyl, C₁-C₁₈-alkoxy, C₂-C₁₀-alkenyl or halogen, in particularfluorine. Preferred examples of substituted and unsubstituted arylradicals are, in particular, phenyl, pentafluorophenyl, 4-methylphenyl,4-ethylphenyl, 4-n-propylphenyl, 4-isopropylphenyl, 4-tert-butylphenyl,4-methoxyphenyl, 1-naphthyl, 9-anthryl, 9-phenanthryl,3,5-dimethylphenyl, 3,5-di-tert-butylphenyl or 4-trifluoromethylphenyl.

The term “heteroaromatic radical” as used in the present text refers to,for example, aromatic hydrocarbon radicals in which one or more carbonatoms are replaced by nitrogen, phosphorus, oxygen or sulfur atoms orcombinations thereof. These may, like the aryl radicals, bemonosubstituted or polysubstituted by linear or branched C₁-C₁₈-alkyl,C₂-C₁₀-alkenyl or halogen, in particular fluorine. Preferred examplesare furyl, thienyl, pyrrolyl, pyridyl, pyrazolyl, imidazolyl, oxazolyl,thiazolyl, pyrimidinyl, pyrazinyl and the like, and also methyl-,ethyl-, propyl-, isopropyl- and/or tert-butyl-substituted derivativesthereof.

The term “arylalkyl” as used in the present text refers to, for example,aryl-comprising substituents whose aryl radical is linked via an alkylchain to the corresponding remainder of the molecule. Preferred examplesare benzyl, substituted benzyl, phenethyl, substituted phenethyl and thelike.

The terms fluoroalkyl and fluoroaryl mean that at least one hydrogenatom, preferably more than one and a maximum of all hydrogen atoms, ofthe corresponding substituent have been replaced by fluorine atoms.Examples of fluorine-comprising substituents which are preferredaccording to the invention are trifluoromethyl, 2,2,2-trifluoroethyl,pentafluorophenyl, 4-trifluoromethylphenyl, 4-perfluoro-tert-butylphenyland the like.

Preference is given to a process for preparing metallocenes of theformula (III) in which the metallocenes of the formula (III) arebridged, i.e. m=1, in particular silicon-bridged metallocenes of groupsof 4 to 6, in particular group 4, of the Periodic Table of the Elements.

Particular preference is given to a process for preparing metallocenesof the formula (III) as described above in which two differentlysubstituted cyclopentadienyl derivatives of the formulae (I) and (I′)and/or their double bond isomers or a bridged biscyclopentadienylderivative of the formula (II) and/or its double bond isomers havingdifferently substituted cyclopentadienyl radicals are used.

The synthesis of the metallocenes of the formula (III) is known inprinciple and can be carried out, for example, by methods analogous tothose described in EP 0 574 597 or EP 0 704 454.

It is usual to react a suitable transition metal source, e.g. zirconiumtetrachloride, with the desired ligands, e.g. two equivalents ofcyclopentadienyl ligand in the form of its lithium salt. To synthesizeansa-metallocenes, i.e. metallocenes having a bridgedbiscyclopentadienyl ligand, the desired cyclopentadienyl radicals arefirstly joined to one another and subsequently reacted, usually afterprior deprotonation, with the transition metal source. WO 2001/48034 andWO 2003/045964 describe, for example, the syntheses of bridgedbiscyclopentadienyl-metallocenes having two different cyclopentadienylradicals of the formulae (I) and (I′)

where the indices are as defined above.

The above-described synthesis scheme is illustrated by the followingexample, which does not, however, restrict the invention, of ametallocene of the formula (III) using two differently substitutedcyclopentadienyl derivatives of the formulae (I) and (I′) in thesynthesis.

The process of the invention usually forms, as mentioned at the outset,not only the desired bridged rac-metallocenes of the formula (III) butalso the corresponding meso compounds, with the terms meso and racreferring to the three-dimensional arrangement of the twocyclopentadienyl ring systems relative to one another. For example, incases in which the two substituted cyclopentadienyl radicals on thebridge are not identical, there is no rac form having C₂ symmetry ormeso form having C_(s) symmetry, but instead there are onlydiastereomeric compounds having C₁ symmetry. When these differentdiastereomeric metallocene compounds which differ from one another inthe three-dimensional arrangement of the differing substituents are usedas catalyst component in the polymerization of propylene, they behave,purely on the basis of the three-dimensional arrangement of the twosubstituted cyclopentadienyl ligands relative to one another, like theC₂-symmetric rac isomer (isotactic polypropylene) or like theC_(s)-symmetric meso isomer (atactic polypropylene) of anansa-metallocene having two identically substituted cyclopentadienylligands and can thus each be designated as a pseudo-rac form or apseudo-meso form.

In the following, rac and pseudo-rac form or meso and pseudo-meso formare distinguished only as rac and meso form.

The separation of the diastereomers, in particular the isolation andpurification of the rac form, is known in principle.

In the synthesis of the bridged ligand system, in the preparation of themetallocene mixture and finally in the purification of the desiredmetallocene isomer, filtrates, mother liquors, reaction residues and/orwork-up residues which comprise the cyclopentadienyl derivatives of theformulae (I) or (I′) or bridged biscyclopentadienyl derivatives of theformula (II) are obtained. These fractions which comprise startingmaterials and/or intermediates and were hitherto usually disposed of aresubjected, separately from one another or after having been combinedand/or after further work-up steps such as a bridge eliminationreaction, to liquid-solid chromatography in order to obtain purifiedcyclopentadienyl derivatives of the formulae (I), (I′) and/or (II) ortheir double bond isomers which are subsequently reused in the processof the invention for preparing metallocenes.

The method of liquid-solid chromatography is known in principle. Asstationary phase, it is possible to use both organic and inorganicfinely divided solids such as aluminum oxides, silica gels, magnesiumsilicates, kieselguhr, activated carbon, cellulose, cellulose triacetateor silica gels modified with organic radicals, in particular hydrocarbonradicals, known as reversed phase materials. The choice of the solventsor solvent mixtures used as liquid mobile phase in the chromatographicmethod is known in principle to those skilled in the art and can bedetermined by means of a few routine thin-layer-chromatographicseparation tests for the respective separation problem.

The stationary phase is usually introduced into separation columns, i.e.cylindrical vessels or tubes which frequently comprise glass orstainless steel and have openings at both end faces which usually have asmaller diameter than the internal diameter of the column itself. Themobile phase can flow through the solid phase under the action ofgravity or with the aid of a deliberately generated superatmosphericpressure.

Very particular preference is given to a process for preparingmetallocenes of the formula (III) as described above in which a reversedphase material is used as stationary phase in the chromatographicpurification of the cyclopentadienyl derivatives of the formulae (I) and(I′) and/or their double bond isomers or the bridged biscyclopentadienylderivatives of the formula (II) and/or their double bond isomers, inparticular in the purification of the cyclopentadienyl derivatives ofthe formulae (I) and (I′) and/or their double bond isomers. Reversedphase materials are commercially available, for example LiChroprepRP-18-end-capped silica gels from Merck. Basic information on reversedphase silica gels is also given in J. Chem. Educ. 1996, 73, A26.

Special preference is given to a process for preparing metallocenes ofthe formula (III), in particular silicon-bridged metallocenes, asdescribed above in which the cyclopentadienyl derivatives of theformulae (I) and (I′) and/or their double bond isomers are recoveredfrom the filtrates, mother liquors, reaction residues and/or work-upresidues obtained in the preparation of metallocenes and/or in thepreparation of bridged, in particular silicon-bridgedbiscyclopentadienyl ligands by subjecting these filtrates, motherliquors, reaction residues and/or work-up residues, either together orindependently of one another, preferably together, to a single ormultiple, acidic or basic, in particular basic, aqueous treatment inwhich any bonds present between bridging silicon atoms andcyclopentadienyl rings are cleaved, and subsequently isolating and ifappropriate concentrating the organic phase comprising thecyclopentadienyl derivatives of the formulae (I) and (I′) and/or theirdouble bond isomers in order for them to be able to be purified furtherin the above-described liquid-solid chromatography.

FIG. 1 schematically shows an example of a preferred embodiment of theprocess of the invention for preparing bridged, in particularsilicon-bridged, metallocenes of the formula (III), in particular fromtwo differently substituted cyclopentadienyl derivatives of the formulae(I) and (I′).

From cyclopentadienyl derivatives of the formulae (I) and (I′), with thetwo cyclopentadienyl derivatives being identical or different, inparticular different, a silicon-bridged biscyclopentadienyl derivativeof the formula (II) is prepared by known methods. For example, twoequivalents of a cyclopentadienyl anion are reacted in a bridgingreaction with an appropriate silicon-comprising bridging reagent, forexample a diorganodichlorosilane such as dimethyldichlorosilane. As analternative, the anion of a cyclopentadienyl derivative of the formula(I) is firstly reacted with an appropriate silicon-comprising bridgingreagent, for example a diorganodichlorosilane such asdimethyldichlorosilane, to form a monocyclopentadienyl derivative whichcomprises a bridging group, for example amonochloromonocyclopentadienyldiorganosilane compound, and the secondleaving group of the bridging group in this compound, for example thechlorine, is subsequently replaced by a further cyclopentadienyl radicalwhich is generated by deprotonation of a cyclopentadienyl derivative ofthe formula (I′) and can be different from the first cyclopentadienylradical to give the desired uncharged bridged cyclopentadienyl compoundof the formula (II). In the isolation and purification of thebiscyclopentadienyl derivative of the formula (II), the filtrate 0 isusually obtained.

In the next step, the biscyclopentadienyl derivative of the formula (II)is usually doubly deprotonated by means of a strong base andsubsequently reacted directly or after prior isolation with a suitabletransition metal compound such as zirconium tetrachloride or one of themodified, rac-selective transition metal sources described in WO1999/15538, WO 2000/31091 or WO 2005/108408 to give a metallocene of theformula (III).

Strong bases which can be used for deprotonating the cyclopentadienylderivatives of the formulae (I) and (I′) or the biscyclopentadienylderivative of the formula (II) are, for example, organometalliccompounds or metal hydrides, preferably compounds comprising an alkalimetal or an alkaline earth metal. Preferred bases are organolithium ororganomagnesium compounds such as methyllithium, n-butyllithium,sec-butyllithium n-butyl-n-octylmagnesium or dibutylmagnesium, inparticular n-butyllithium or methyllithium.

The deprotonation of the cyclopentadienyl derivatives of the formulae(I) and (I′) or the biscyclopentadienyl derivative of the formula (II)is usually carried out in the temperature range from −78° C. to 110° C.,preferably from 0° C. to 80° C. and particularly preferably from 20° C.to 70° C. Suitable inert solvents in which the deprotonation of thecyclopentadienyl derivatives by means of strong bases can be carried outare aliphatic or aromatic hydrocarbons such as benzene, toluene, xylene,mesitylene, ethylbenzene, cumene, decalin, tetralin, pentane, hexane,cyclohexane, heptane or ethers such as diethyl ether, di-n-butyl ether,tert-butyl methyl ether (MTBE), tetrahydrofuran (THF),1,2-dimethoxyethane (DME), anisole, triglyme, dioxane and also anymixtures of these. Preference is given to solvents or solvent mixturesin which the preparation of the metallocene complexes of the formula(III) can likewise be carried out directly. After the reaction of thebiscyclopentadienyl bisanion with a transition metal compound bearingtwo leaving groups, for example zirconium tetrachloride, a suspension inwhich the metallocene of the formula (III) is present as a solid can beobtained directly, as described, for example, in EP 0 576 970 or EP 0574 597. The product-comprising solid is then isolated by filtration anda further filtrate 1, which can be combined with the filtrate 0, isobtained.

In the further purification of the metallocene of the formula (III) byremoval of salts such as lithium chloride or magnesium chloride andremoval of undesirable metallocene isomers, in particular the meso form,further residues which are referred to as filtrate 2 are obtained. Thepurification is preferably carried out by a method as described in EP 0780 396. As an alternative, the metallocene can be separated from thesalt by extraction with an organic solvent, for example methylenechloride, and freed of further undesirable by-products bycrystallization and be obtained in purified form. In all cases,filtrates are obtained in addition to the isolated metallocenes of theformula (III).

The filtrates 0, 1 and 2 are preferably combined and treated withaqueous acid or base, in particular aqueous base, to cleave thesilicon-cyclopentadienyl carbon bond. The cleavage reaction ispreferably carried out at a temperature of from 0° C. to 200° C.,particularly preferably from 20° C. to 150° C., in particular from 50°C. to 110° C. The reaction can be carried out under atmospheric pressureor under superatmospheric pressure.

Suitable bases are, in particular, alkali metal hydroxide and alkalineearth metal hydroxides. Preference is given to using sodium hydroxide orpotassium hydroxide, in particular sodium hydroxide. The addition ofphase transfer catalysts such as tetraalkylammonium salts or crownethers such as 18-crown-6 can help to accelerate the cleavage reaction.

The molar ratio of bridged ligand, in particular silicon-bridged ligand,to hydroxide is usually from 1:0.1 to 1:100, preferably from 1:1 to1:20, in particular from 1:2 to 1:10.

The presence of various organic solvents in the reaction mixture isunproblematical, as long as these solvents are inert toward thereactants and the desired products, for example the cyclopentadienylderivatives of the formulae (I) and (I′), under the reaction conditions.

After carrying out the cleavage reaction, the reaction mixture isneutralized or made slightly acidic, the aqueous phase is separated offand discarded and the organic phase, which comprises cyclopentadienylderivatives of the formulae (I) and (I′), is dried if appropriate, forexample by means of magnesium sulfate, and subsequently concentrated tothe extent necessary for the subsequent chromatographic purification.The chromatography is, as described above, a solid-liquidchromatography.

The purified, recovered cyclopentadienyl derivatives of the formulae (I)and (I′) are finally reused together with the appropriate, necessaryamounts of freshly prepared cyclopentadienyl derivatives of the formulae(I) and (I′) in the renewed preparation of a metallocene of the formula(III).

The present invention further provides a process for recoveringcyclopentadienyl derivatives of the formula (I) and/or their double bondisomers, as described above, from the filtrates, mother liquors,reaction residues and/or work-up residues obtained in the preparation ofsilicon-bridged metallocenes and/or in the preparation ofsilicon-bridged biscyclopentadienyl ligands using such cyclopentadienylderivatives, wherein these filtrates, mother liquors, reaction residuesand/or work-up residues, either together or independently of oneanother, preferably together, are subjected to a single or multiple,acidic or basic, in particular basic, aqueous treatment in which bondsbetween bridging silicon atoms and cyclopentadienyl rings are cleaved,and subsequently isolating and if appropriate concentrating the organicphase comprising the cyclopentadienyl derivatives of the formulae (I)and (I′) and/or their double bond isomers in order for them to be ableto be purified further in liquid-solid chromatography.

The present invention further provides for the use of recycled,substituted cyclopentadienyl derivatives of the formulae (I) and (I′)and/or their double bond isomers or bridged biscyclo-pentadienylderivatives of the formula (II) and/or their double bond isomers, asdescribed above, which have been purified by means of liquid-solidchromatography in the synthesis of metallocenes, in particularmetallocenes of the formula (III), wherein the substitutedcyclo-pentadienyl derivatives are recovered from the filtrates, motherliquors, reaction residues and/or work-up residues obtained in thepreparation of metallocenes and/or in the preparation of bridgedbiscyclopentadienyl ligands.

The present invention likewise provides for the use of liquid-solidchromatography, in particular liquid-solid chromatography using reversedphase materials as stationary phase, for purifying substitutedcyclopentadienyl derivatives of the formulae (I) and (I′) and/or theirdouble bond isomers or bridged biscyclopentadienyl derivatives of theformula (II) and/or their double bond isomers, as described above, forpreparing metallocenes, in particular metallocenes of the formula (III),wherein the substituted cyclopentadienyl derivatives to be purified arerecovered from the filtrates, mother liquors, reaction residues and/orwork-up residues obtained in the preparation of metallocenes and/or inthe preparation of bridged biscyclopentadienyl ligands.

The metallocenes of the formula (III) prepared by the process of theinvention can be used together with suitable cocatalysts and, ifappropriate, suitable support materials as constituent of a catalystsystem for the polymerization of olefins.

The invention is illustrated by the following examples which do not,however, restrict the scope of the invention.

EXAMPLES General

The synthesis and handling of organometallic compounds was carried outwith exclusion of air and moisture under argon (glove box and Schlenktechnique).

2-isopropyl-4-(4′-tert-butylphenyl)-1-indene and2-methyl-4-(4′-tert-butylphenyl)-1-indene were prepared by methodsanalogous to those described in WO 9840331 and WO 0148034.

Example 1 Synthesis ofdimethylsilanediyl(2-methyl-4-(4′-tert-butylphenyl)-1-indene)(2-isopropyl-4-(4′-tert-butylphenyl)-1-indene)(1) a) Preparation of2-isopropyl-4-(4′-tert-butylphenyl)-1-indenyldimethylchlorosilane (1a)

7.4 ml (61 mmol) of dimethyldichlorosilane (DMDCS) were added at −40° C.to a solution of 2-isopropyl-4-(4′-tert-butylphenyl)indenyllithium whichhad been obtained by reacting 5.84 g (20.1 mmol) of2-isopropyl-4-(4′-tert-butylphenyl)-1-indene dissolved in 50 ml oftoluene and 2.57 ml (40 mmol) of tetrahydrofuran (THF) with 8.65 ml(23.1 mmol) of n-butyllithium (2.68 M in toluene). The reaction mixturewas stirred overnight at room temperature. Excess DMDCS and THF weresubsequently distilled off under reduced pressure and lithium chloridewas filtered off with the aid of a glass filter frit. This gave 7.7 g(20.1 mmol) of (1a) in 20 g of toluene.

b) Preparation of2-dimethylsilanediyl(2-methyl-4-(4′-tert-butylphenyl)-1-indene)(2-isopropyl-4-(4′-tert-butylphenyl)-1-indene)(1)

4.85 g (18.5 mmol) of 2-methyl-4-(4′-tert-butylphenyl)-1-indenedissolved in 45 g of toluene and 3 ml (37 mmol) of THF were deprotonatedby means of 6.93 ml (18.5 mmol) of n-butyllithium (2.68 M in toluene) at45° C. The reaction mixture was stirred at 45° C. for 1 hour, and thesolution of 7.7 g (20.1 mmol) of (1a) in 20 g of toluene prepared inexample 1a) was subsequently added. The reaction mixture was stirred at60° C. for 3 hours and quenched by addition of 100 g of water. After acustomary work-up, the organic phase was evaporated under reducedpressure and the oil obtained (12 g, mixture of ligand (1), the twoindenes used and some impurities) was crystallized after addition of 30g of methanol with vigorous stirring. Filtration, washing of the filtercake with a little methanol and drying gave 7.2 g of (1) (yield: 65%).The filtrate was partly evaporated and cooled to 0° C. After filtration,a second crystal fraction of the ligand (1) (0.9 g) was isolated (totalyield: 72%).

The methanol-comprising filtrate (15 g of filtrate 0) was used as shownin the scheme of FIG. 1 for the “neutralization” of the filtrate 1obtained in the preparation of the crude metallocene product.

HPLC analysis of filtrate 0 indicated the following composition:

2-Methyl-4-(4′-tert- 5.6% by weight → 0.84 g (3.2 mmol)butylphenyl)-1-indene = 2-Isopropyl-4-(4′-tert- 9.7% by weight → 1.45 g(5 mmol) butylphenyl)-1-indene = Ligand (1) =   5% by weight → 0.75 g(1.23 mmol)

Example 2 Synthesis ofrac-dimethylsilanediyl(2-methyl-4-(4′-tert-butylphenyl)-1-indenyl)(2-isopropyl-4-(4′-tert-butylphenyl)-1-indenyl)zirconiumdichloride (2) a) Preparation of the Mixture of Rac/Meso Complexes (2a)

8.32 g (26 mmol) of n-butyllithium (20% by weight in toluene) were addedat room temperature to a solution of 8.0 g (13.1 mmol) of ligand (1) in100 g of toluene and 4.5 g of THF under protective gas (nitrogenatmosphere). The reaction mixture was stirred at 80° C. for 2 hours andsubsequently cooled to 25° C. A suspension of 3.33 g (14.3 mmol) ofzirconium tetrachloride in 6 g of toluene was added to this solution ofthe deprotonated ligand (1). This resulted in the temperature rising to45° C. The reaction mixture was stirred at 45° C. for 2 hours, and afterthe suspension formed had been cooled to room temperature, thesuspension was filtered through an invertible glass frit filter. Thefilter cake, a mixture of lithium chloride and metallocene, was washedtwice with a total of 10 g of toluene.

The filtrate was evaporated to a volume of about 25 ml at about 48° C.under reduced pressure. A second fraction of metallocene crystallizedfrom the solution. After filtration and washing of the second fractionwith 4 g of toluene, the two isolated fractions of the metallocene werecombined and dried under reduced pressure. The total yield ofmetallocene-comprising crude product (2a) was 8.1 g.

The methanol-comprising filtrate 0 from example 1 was combined with thefiltrates from example 2a) (filtrate 1), resulting in any residualbutyllithium present in filtrate 1 being destroyed.

b) Purification of (2a) to giverac-dimethylsilanediyl(2-methyl-4-(4′-tert-butylphenyl)-1-indenyl)(2-isopropyl-4-(4′-tert-butylphenyl)-1-indenyl)zirconiumdichloride (2)

8.1 g of crude product (2a) were suspended in a solvent mixturecomprising 64.31 g of acetone, 17.66 g of water, 0.49 g of THF and 8.75g of toluene at 15° C. and after 5 minutes the rac/meso ratio wasdetermined at this point in time by means of ¹H-NMR. The suspension wassubsequently heated to 20° C. and the change in the rac/meso ratio wasmonitored by means of ¹H-NMR spectroscopy. After 2.5 hours at 20° C.,the rac/meso ratio was greater than 20. The suspension was filteredthrough an invertible glass frit filter. The filter cake was washed fourtimes with a total of 15 g of toluene and dried in a stream of nitrogen.

The isolated metallocene was suspended in 25 g of toluene at 25° C. andafter stirring for two hours was isolated again by filtration and dryingunder reduced pressure. The yield of pure metallocene (2) was 2.3 g(22.8%).

All filtrates obtained in example 2b) were combined to form filtrate 2(see FIG. 1). 190 g of filtrate 2 were obtained.

Example 3 Work-Up of the Combined Filtrates

2.62 g (65.5 mmol) of sodium hydroxide powder were added to the combinedfiltrates (filtrate 0, filtrate 1 and filtrate 2) from examples 1, 2aand 2b. The reaction mixture was refluxed for 3 hours. The reactionmixture was subsequently acidified with 50.4 g of 20% aqueous sulfuricacid (102.8 mmol). After phase separation, the organic phase was washedwith 40 g of water, dried over magnesium sulfate and subsequentlyconcentrated. This gave 9.2 g of a viscous oil.

HPLC analysis: 2-methyl-4-(4′-tert- 40.2% => 3.7 g (14.1 mmol)butylphenyl)-1-indene: 2-isopropyl-4-(4′-tert- 49.5% => 4.55 g (15.7mmol) butylphenyl)-1-indene

The viscous oil was fractionated by means of preparative HPLC (reversedphase chromatography column; 120 g of C18-end-capped SiO₂;acetonitrile/water (80/20); gradientless (isocratic) elution conditions;UV detector (235 nm)).

Three fractions were collected:

-   -   1) pure 2-methyl-4-(4′-tert-butylphenyl)-1-indene    -   2) mixture of the indenes    -   3) pure 2-isopropyl-4-(4′-tert-butylphenyl)-1-indene

Removal of the solvents gave 2.73 g of pure2-methyl-4-(4′-tert-butylphenyl)-1-indene (74%), 2.5 g of pure2-isopropyl-4-(4′-tert-butylphenyl)-1-indene (55%) and 3.5 g of themixed fraction comprising about 30% of2-methyl-4-(4′-tert-butylphenyl)-1-indene and about 70% of2-isopropyl-4-(4′-tert-butylphenyl)-1-indene. The recovered pure indeneswere used for the renewed preparation of the bridged ligand (1) in amanner analogous to example 1.

Example 4 Synthesis ofdimethylsilanediyl(2-methyl-4-(4′-tert-butylphenyl)-1-indene)(2-isopropyl-4-(4′-tert-butylphenyl)-1-indene) (1) Using the IndenesRecovered in Example 3

Using a method analogous to example 1, ligand (1) was prepared from 5.85g of 2-isopropyl-4-(4′-tert-butylphenyl)-1-indene (2.4 g of recoveredindene from example 3 and 3.45 g of indene from a fresh synthesis) and4.85 g of 2-methyl-4-(4′-tert-butylphenyl)-1-indene (2.25 g of recoveredindene from example 3 and 2.6 g of indene from a fresh synthesis).Work-up and crystallization gave 8.2 g of ligand (1).

1. A process for recycling metallocene catalyst components, comprising:(a) recovering a cyclopentadienyl or a bridged biscyclopentadienylderivative from a filtrate, mother liquor, reaction residue, and/or awork-up residue obtained in the preparation of a metallocenes and/or inthe preparation of a bridged biscyclopentadienyl ligand; and (b)purifying the recovered derivative by liquid-solid chromatography;wherein the cyclopentadienyl derivatives are recovered from thefiltrates, mother liquors, reaction residues and/or work-up residuesobtained in the preparation of metallocenes and/or in the preparation ofbridged biscyclopentadienyl ligands by subjecting these filtrates,mother liquors, reaction residues and/or work-up residues, eithertogether or independently of one another, to a single or multiple,acidic or basic aqueous treatment in which any bonds present betweenbridging silicon atoms and cyclopentadienyl rings are cleaved, andsubsequently isolating and, optionally, concentrating the organic phasecomprising the cyclopentadienyl derivatives in order for them to be ableto be purified further in the liquid-solid chromatography.
 2. Theprocess of claim 1 wherein the recovered derivative is used to prepare ametallocene.
 3. The process of claim 1 wherein the filtrates, motherliquors, reaction residues and/or work-up residues containing a mixtureof two differently substituted cyclopentadienyl derivatives or a bridgedbiscyclopentadienyl derivative having differently substitutedcyclopentadienyl radicals are used in step (a).
 4. The process of claim1 wherein a reversed phase material is used as stationary phase in thechromatographic purification of the cyclopentadienyl or bridgedbiscyclopentadienyl derivatives.
 5. The process of claim 1 wherein thecyclopentadienyl derivative has the formulae (I) or (I′)

or the bridged biscyclopentadienyl derivative has the formula (II)

where R¹, R^(1′) are identical or different and are each an organicradical having from 1 to 40 carbon atoms, R², R^(2′) are identical ordifferent and are each hydrogen or an organic radical having from 1 to40 carbon atoms, or R¹ with R² and/or R^(1′) with R^(2′) together withthe atoms connecting them in each case form a monocyclic or polycyclic,saturated or unsaturated, substituted or unsubstituted ring system whichhas from 3 to 40 carbon atoms and has a ring size of from 5 to 12 atomsand may also comprise heteroatoms selected from the group consisting ofthe elements, Si, Ge, N, P, As, Sb, 0, S, Se or Te, T, T′ are identicalor different and are each a divalent organic group which has from 1 to40 carbon atoms and together with the cyclopentadienyl ring in each caseforms at least one further saturated or unsaturated, substituted orunsubstituted ring system having a ring size of from 5 to 12 atoms,where T and T′ within the ring system fused to the cyclopentadienyl ringmay comprise the heteroatoms Si, Ge, N, P, As, Sb, O, S, Se or Te, and Zis a bridge between the two substituted cyclopentadienyl ligands whichconsists of a divalent atom or a divalent group.
 6. The process of claim1 wherein one or more of the products isolated from the liquid-solidchromatography are used to prepare a metallocene of the formula (III)

wherein M is Group 3, 4, 5 or 6 element, the radicals X are identical ordifferent and are each an organic or inorganic radical, with tworadicals X also being able to be joined to one another, n is 0, 1, 2 or3, and m is 0 or
 1. 7. The process of claim 6, wherein the metalloceneis a silicon-bridged Group 4 to 6 metallocene.